In vitro modulation of the human gut bacterial community by crude polysaccharides from cultivated mushrooms Lentinus polychrous and Lentinus squarrosulus

Background Edible mushroom polysaccharides are recognized as prebiotics that influence gut microbiota composition and host health. However, the effects of the polysaccharides from Lentinus squarrosulus and Lentinus polychrous on the human gut bacterial community remain poorly understood. To address this gap, the present study evaluated the effects of crude polysaccharide extracts from cultivated mushrooms on the human fecal bacterial community using an in vitro batch fermentation model. Methods Species identification of the two mushroom isolates (PB1 and LP1) was performed using molecular techniques. Cultivated mushrooms served as a source of polysaccharides, which were extracted using a combination of sonication and hot water. The composition of crude polysaccharides, including total carbohydrates, reducing sugars, proteins, and phenolic compounds, was analyzed. These extracts were subjected to simulated gastrointestinal digestion and used as substrates in batch fermentation inoculated with human fecal slurry. The bacterial communities in the treatment groups were identified and analyzed using 16S rRNA gene amplicon sequencing. Results PB1 and LP1 were identified as L. squarrosulus PB1 and L. polychrous LP1, respectively. Composition analysis revealed that the crude polysaccharides LS and LP derived from L. squarrosulus PB1 and L. polychrous LP1, respectively, were primarily composed of polysaccharides with low levels of protein, reducing sugars, and phenolic compounds. After the simulated gastrointestinal digestion, LS and LP exhibited high resistance, suggesting that they may reach the colon for microbial fermentation. Fermentation of LS and LP modulated the gut microbiota by increasing the abundance of beneficial genera such as Bacteroides and Parabacteroides. A notable increase in the relative abundance of Fusobacterium was observed. However, its functional role requires further investigation. Additionally, fermentation with LS or LP reduced both Firmicutes/Bacteroidota and Blautia/Bacteroides ratios. Fermentation also resulted in a decrease in pH. Conclusions Crude polysaccharides from cultivated L. squarrosulus PB1 and L. polychrous LP1 can modulate the human fecal bacterial community by enriching beneficial bacteria, highlighting their potential to improve gut health. Further research is needed to elucidate how the specific characteristics of these polysaccharides, particularly their structure, influence the gut microbiota and assess their implications for human health.